1. Field of the Invention
The present invention relates to a burner for operating a heat generator.
2. Discussion of Background
EP-0 780 629 A2 has disclosed a burner which comprises a swirl generator on the incident-flow side, the flow formed herein being passed smoothly into a mixing section. This is done with the aid of a flow geometry, which is formed at the start of the mixing section for this purpose and consists of transition passages which cover sectors of the end face of the mixing section, in accordance with the number of acting sectional bodies of the swirl generator, and run helically in the direction of flow. On the outflow side of these transition passages, the mixing section has a number of prefilming bores, which ensure that the flow velocity along the tube wall is increased. This is then followed by a combustion chamber, the transition between the mixing section and the combustion chamber being formed by a jump in cross section, in the plane of which a backflow zone or backflow bubble forms.
The swirl intensity in the swirl generator is therefore selected in such a way that the breakdown of the vortex does not take place inside the mixing section but further downstream, as explained above, in the region of the jump in cross section. The length of the mixing section is dimensioned in such a way that an adequate mixture quality is ensured for all types of fuel.
Although this burner, compared with those from the prior art, guarantees a significant improvement with regard to intensification of the flame stability, lower pollutant emissions, lower pulsations, complete burn-out, large operating range, good cross-ignition between the various burners, compact type of construction, improved mixing, etc., it has been found that this burner has no autonomous measures in order to be able to reliably run the gas turbine in particular in its transient load ranges. For example, in the part-load range, the burner must be assisted with a back up flame. In this case, the integration of such measures in the burner must not lead to any additional pollutant emissions, which could jeopardize the operational and emissive advantages of the burner taken as a basis. There is also the fact that these burners, in gas turbines, are ignited in a conventional manner by means of a special igniter. These igniters usually operate at a high voltage, which delivers the ignition spark, which either serves directly as ignition source at high output or ignites an ignition torch. These igniters require a separate leadthrough and seal for the igniter and its conduits through the casing of the gas turbine right into the combustion chamber. However, the existing igniter systems have the following disadvantages:
a) costly separate leadthrough and seal for the igniter and its conduits through the casing of the gas turbine right into the combustion chamber; PA1 b) cross-ignition inside the combustion chamber on account of the small number of igniters (usually only 1 igniter for reasons of cost); PA1 c) thermal loading of the igniter due to the positioning in the combustion chamber, which, for example, requires cooling of the igniter, for which reason leakages occur due to seals which may be unsound; PA1 d) highly susceptible to condensed water, in which case short circuits divert the ignition spark.